A multimedia service refers to, for example, a conversational service, such as a video phone, a streaming service, such as a Video On Demand (VOD) service, a multicast or broadcast service, or the like. A real time multimedia service can be divided into a conversational service, an interactive service, a streaming service, and the like. Further, the real time multimedia service can be divided into a unicast service, a multicast service, and a broadcast service, according to the number of users who participates in the service.
In order to provide a multimedia service, a scheme for providing a QoS in a network may be divided into a Best Effort (BE) scheme, a per-class QoS scheme, and a per-flow QoS scheme.
First, in the BE scheme, no support is provided for QoS. The per-class QoS scheme is a scheme in which packets have different degrees of importance and the packets are processed according to the degrees of the importance in the middle of the network. For example, in the per-class QoS scheme, a QoS control is performed according to a degree of importance, that is, according to a priority, of a corresponding packet, regardless of a flow to which the corresponding packet belongs. In order to support the per-class QoS scheme, a resource reservation between a transmission side and a reception side is not required. For example, the priority may be a loss priority, a delay priority, or the like.
The per-flow QoS scheme may be a scheme for reserving a resource per stream. For example, a resource (for example, a bit rate, or a buffer status) or QoS (i.e., a delay, a loss rate, or the like) is reserved per flow. Here, the flow refers to a stream used for a service. For example, a video stream, an audio stream, and a text stream which are used for providing a VOD service become separate flows, respectively.
In a Universal Mobile Telecommunications System (UMTS) 3rd Generation (3G) of the 3G Partnership Project (3GPP) as well as the Institute of Electrical and Electronics Engineers (IEEE) 802.16 (Wireless Broadband (WiBRO), Worldwide Interoperability for Microwave Access (WIMAX)), and Long Term Evolution (LTE) systems, a standard is established to support a per-class QoS scheme and a per-flow QoS scheme. However, in order to use the QoS scheme, an interface between a media layer of a higher layer and a network layer of a lower layer is needed.
Degrees of importance of video packets are different from packet to packet when using Moving Picture Experts Group-2 (MPEG-2) and H.264, or especially using Scalable Video Coding (SVC). In order to effectively control a QoS of a video service, the difference of the degrees of importance from packet to packet should be recognized. In an IPv6, in order to identify the importance by packet, after 5 tuples including a recipient's address, a sender's address, a port number of a corresponding service in the recipient's apparatus, a port number of a corresponding service in the sender's apparatus, and a protocol to be used are read, header data for identifying degrees of importance of packets should be read. This method needs time for processing each packet, and the independence of the protocol layer is violated. For example, packets should have been processed in a router with IP headers of packets, but it is not possible according to this method.
If degrees of importance by packet can be identified easily, a QoS control in a router may be performed smoothly. For example, if the network status is not good, packets can be removed from a less important packet according to importance of the packets.
Meanwhile, an SVC technique and a Multi-view Video Coding (MVC) technique which are in the process of standardization are based on the H.264/Advanced Video Coding (AVC) standard. Further, a Network Abstraction Layer Unit (NALU) format is also used in the configuration of bit strings of coded data.
FIG. 1 is a diagram illustrating a Video Coding Layer (VCL) and a Network Abstraction Layer (NAL) in H.264/AVC according to the related art.
Referring to FIG. 1, in H.264/AVC, a NAL 120 is defined between a VCL 110 that performs a video encoding process itself and a subsystem 130 that transmits and stores the coded information. Therefore, the VCL and the NAL are separated.
In order to map coded data 111 generated in the VCL, into bit strings for a subsystem, such as an H.264/AVC file format 131, a Real-time Transport Protocol (RTP) 133, or an MPEG-2 system 135, the NAL 120 processes the coded data 111 generated in the VCL, a parameter set, or information, such as Supplemental Enhancement Information (SEI) 113 in a NALU.
The NAL unit is divided into a VCL NAL unit 123 and a non-VCL NAL unit 125. The VCL NAL unit 123 is a NAL unit that corresponds to the coded data 111 generated in the VCL, while the non-VCL NAL unit 125 is a NAL unit that corresponds to a parameter set and information, such as a SEI 113.
The NAL unit basically includes a NAL header and Raw Byte Sequence Payload (RBSP) which is a data part generated as a result of a video compression in a VCL.
FIG. 2 is a diagram illustrating a format of a NAL unit according to the related art.
Referring to FIG. 2, a NAL unit 200 includes a NAL header 210 and a NAL payload 240.
The NAL header 210 generally has a size of 1 to 5 bytes. The NAL header 210 includes NALU type information 220 for indicating a kind of the NAL unit, and Layer Identification Information 230 for identifying a compressed layer of an original data included in the NALU payload.
The NALU type information 220 includes one bit of a fixed bit (F) field 221, two bits of a nal_ref_idc (NRI) field 222 for indicating whether the video is a reference picture or not, and five bits of a NALU type field 223 which is an identifier for indicating a kind of the NAL unit.
The layer identification information 230 may include a combination of a priority, a spatial hierarchy level, a temporal hierarchy level, and/or a quality hierarchy level. For example, the layer identification information 230 may include 8 bits of a priority field (hereinafter referred to as “P”) 231 for indicating priority so that the compressed layer of the original data can be identified, 3 to 8 bits of a Dependency_id field (hereinafter referred to as “D”) 232 for indicating a spatial hierarchy level, 3 to 8 bits of a Temporal_level field (hereinafter referred to as “T”) 233 for indicating a temporal hierarchy level, and 2 to 8 bits of a Quality_level field (hereinafter referred to as “Q”) 234 for indicating a quality hierarchy level.
For reference, the format of the NALU is used in Multi-view Video Coding (MVC). Besides, in MVC, together with the NALU type information 220, instead of the layer identification information 230, view identification information for identifying a view can be included.
According to the format of the NAL unit according to the SVC or MVC of the related art, in order to identify the layer or the view of NAL unit, the layer identification information 230 or the view identification information of the NAL header needs to be parsed. Especially, the layer identification information 230 has a size of 4 bytes or less, and the layer to which the corresponding NAL unit belongs can be determined when values of the P 231, the D 232, the T 233, and the Q 234 are known by parsing the NAL header 210. However, parsing the entire NAL header 210 in order to find out the values of the P 231, the D 232, the T 233, and the Q 234 becomes a burden to a processor, and may be a cause of increasing the cost of a system.
Further, the NAL header 210 includes various kinds of information for identifying importance of packets like the layer identification information 230, such as the D 232, the T 233, and the Q 234 in addition to the NRI field 222 and the Priority field (P) 231. It is difficult to use the information since the relations among the kinds of information are not defined. For example, relating to the D 232, the T 233, and the Q 234 of the layer identification information, when a packet having “1” as a value of the D 232 and a packet having “1” as a value of the T 233 exist, if a relation for expecting a coding process is not understood, hierarchy on the priorities of the two packets may not be identified. Further, a NAL layer in a network of the related art is designed for a video service.
Therefore, for a future media service in which various media components, such as audios, videos, texts, and user interfaces are combined, a need exists for a multimedia abstraction layer which can be abstracted regardless of kinds of media components.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.